Nao Kajishima: A high school boy often mistaken for a girl.

He and his entire class are summoned to another world during class.

The objective is a common cliché: save the world by defeating the Demon Lord in this other world.

However, the goddess announces:

'There's one person too many; I can't send everyone to the other world. Someone will have to give up.'

"What!?"

His classmates panic.

Nao, too, was flustered, but he is suddenly shoved aside by someone.

He somehow manages to cross over to the other world, but one of the powers he obtains there is [Gender Transformation].

He is forced to live by constantly changing between male and female!

And then, in the world he arrived in, he gets further embroiled in madness and ends up becoming the worst Demon Lord in history.

He selfishly twists the lives of many people, brainwashes them to create slaves, and exacts his revenge.